Like a good pop song, if a genre comic is going to keep you interested, it has to have a hook. It really doesn't matter if the art is exceptional, or it has an inventive structure or well-written characters. If it can't be distilled into one intriguing sentence of less than ten words, then it's not going to keep your attention. Blind guy fights crime; orphaned billionaire is world's greatest detective; six guns control the fate of the world; this Avenger is a freaking mess; Teenage Mutant Ninja Turtles, etc. But you can't just have the hook -- a comic with bad art, poor writing, and a fantastic hook is still a mediocre comic.
Dead Letters Vol. 1: The Existential Op by Christopher Sebela and Chris Visions, is far from mediocre, with strong writing, captivating and kinetic art, and a hook that will grab you from the get-go: amnesiac detective joins gang war in Purgatory.